Asteroid may hit Mars next month

Will asteroid 2007 WD5 crash into Mars January 30? Odds it'll happen are now 1 in 75.

Astronomy: Roen Kelly

December 21, 2007A small asteroid discovered November 20 may strike Mars next month.

Astronomers with NASA's Near Earth Object (NEO) Program at the Jet Propulsion Laboratory in Pasadena, California, calculate the odds of a January 30 collision at 1 in 75. While this is remote, it's less so than last week's estimated 1-in-350 chance.

NEO astronomer Steve Chesley, who's used to dealing with million-to-one odds, calls the event "extremely unusual," and, in something of a twist, NEO astronomers are rooting for an impact.

An armada of spacecraft orbiting the Red Planet — the European Space Agency's Mars Express and NASA's Mars Reconnaissance Orbiter and Mars Odyssey — would have ringside seats to view the strike and its after-effects. Even Earth-based telescopes could potentially observe the impact because Mars is near opposition and, therefore, unusually close.

Astronomers say asteroid 2007 WD5 is about 160 feet (50 meters) across. If it struck Mars, the energy would be similar to the 1908 Tunguska blast in Siberia, where a stony asteroid exploded above the taiga. The blast felled and scarred trees over 810 square miles (2,100 square km).

One difference: Tunguska was an air burst and left no crater, whereas 2007 WD5 likely would reach Mars' surface intact.